Future of factor XI inhibitors in cardiovascular practice.

Anticoagulation is indicated for treatment and prevention of arterial and venous thrombosis. Targeting different steps of the coagulation process, currently available anticoagulants entail an increased risk of bleeding, which detrimentally impacts on prognosis and hinders the administration of an effective antithrombotic regimen. Factor XI (FXI) inhibition has emerged as a strategy to uncouple prevention of thrombosis from bleeding. Indeed, while FXI is crucial for the amplification phase in pathological thrombosis, it is ancillary in physiological hemostasis. A comprehensive search in several scientific databases has been performed to identify relevant studies in the field. In addition, ongoing trials have been searched for in proper datasets to provide an updated and comprehensive assessment of the current state of investigations on FXI inhibition. Many compounds have been tested to inhibit FXI at different stages (i.e., synthesis, activation, or interactions with target molecules and coagulation factors). These include antisense oligonucleotides, monoclonal antibodies, small molecules, natural peptides and aptamers. In phase 2 studies, FXI inhibitors reduced thrombotic complications without any corresponding increase in bleeding. FXI inhibitors were noninferior and potentially superior to low-molecular-weight heparin in orthopedic surgery and reduced bleeding compared to apixaban in patients with atrial fibrillation. FXI inhibition is also under testing in other conditions, including end-stage renal disease, cancer, or noncardioembolic stroke. FXI inhibition represents a promising and rapidly emerging approach for a number of clinical indications. This article reviews the rationale, evidence, pharmacology, and future applications of FXI inhibition.